Core barrel



Sept. 22, 1959 A. P. SHEPARD 1n 2,905,444

y f CORE BARREL y Filed July 26, 1957 Ew Y" @4MM ATTORNEY United States Patent O CORE BARREL Application July 26, 1957, Serial No. 674,446

` z Claims. (ci. 2ss-7z) This invention relates to a core barrel, and it concerns more particularly a core barrel for use, in conjunction with a core bit, in obtaining samples of subsurface earth formations from well bores.

The invention contemplates la core barrel of a type which is capable of being dropped from the surface, through the drill pipe, and automatically seating itself in the core bit and latching itself in engagement with the drill collar, and which is capable of being retrieved upon completion of the coring operation.

The principal object of the invention is to provide a core barrel having a chamber therein for the storage of liquefied gas, and means carried by the core barrel and operable in response to predetermined external pressures existing at the bottom of a well bore, consisting in part of the static pressure of the well fluids, including the drilling fluid, whereby a stream of the liquefied gas is released, and is discharged from the lower end of the core barrel, as the core barrel approaches the bottom of the well bore.

Another object of the invention is to provide a core barrel of the type described in which the stream of liquefied gas discharged from the lower end of the core barrel serves to cool the core bit; in conjunction with a circulating stream of drilling fluid, to remove the cuttings from the hole; to freeze the bottom of the hole ahead of the core bit; to keep the core already drilled frozen; and to prevent the drilling fluid from coming in contact with the newly drilled surface until the coring operation is completed.

Another object of the invention is to provide a core barrel having a high pressure chamber therein for the storage of compressed normally gaseous fluid, a low pressure chamber positioned below the high pressure chamber for the storage of liquefied gas maintained at a lower pressure, a fluid passage communicating at its ends with the high and low pressure chambers, an open ended core receiving chamber positioned below the low pressure chamber, a fluid passage communicating at its ends with the low pressure chamber and the core receiving chamber, a diaphragm valve in the fluid passage between the high pressure chamber and the low pressure chamber and operable in response to predetermined external pressures existing in a well bore, consisting in part of the static pressure of the well fluids, including the drilling fluid, whereby a stream of liquefied gas is continuously released from the high pressure chamber and passes through the low pressure chamber, and is discharged into the core receiving chamber, as the core barrel approaches the bottom of the well bore, and a check valve in the fluid passage between the low pressure chamber and the core receiving chamber.

The invention will be readily understood by referring to the following description and the accompanying drawing, in which Figs. 1A, 1B and 1C together comprise an elevational view, partly in section taken on a medium line, of a core barrel embodying the invention.

Referring to the drawing, the core barrel of the invention includes an elongated, vertically disposed cylindrical casing 1, which for convenience in manufacturing and assembling may be formed in sections as desired. A lower section of the casing 1, comprising an inner shoe 2 and an outer shoe 3, is capable of being seated in a core bit (not shown), and an upper section of the casing, designated by the numeral 4, is provided with latch means (not shown) for engagement with the drill collar.

A high pressure storage chamber 5 is positioned in the casing l, below the upper section 4, for the storage of compressed normally gaseous fluid such as air, nitrogen, or carbon dioxide. A low pressure chamber 6 is positioned below the high pressure chamber 5 for the storage of liquefied gas maintained at a lower pressure. An open ended core receiving chamber 7 is positioned belowthe low pressure chamber 6, adjacent the inner set shoe 2.

A core catching device comprising a plurality ofrcircumferentially spaced resilient ngers 8 is positioned in the inner set shoe 2 below the core receiving chamber 7.

A diaphragm valve 9 is operatively positioned between the high pressure chamber 5 and the low pressure chamber 6, in fluid communication therewith, and is operable in response to predetermined external pressures existing in a well bore, consisting in part of the static pressure of the well fluids, including the drilling fluid, whereby a stream of liquefied gas is continuously released from the high pressure chamber 5 and passes through the low pressure chamber 6, and is discharged into the core receiving chamber 7, as the core barrel approaches the bottom of the well bore. A check valve 10 is operatively positioned between the low pressure chamber 6 and the core receiving chamber 7, in fluid communication therewith.

A valve 11 is provided above the storage chamber 5 for use in filling the high pressure chamber 5 with compressed normally gaseous fluid. The Valve 11 is in fluid communication with a fluid passage 12 formed in a connecting member 13, which comprises the upper end of the high pressure chamber 5.

The diaphragm valve 9 is connected to the high pressure chamber 5 by a flexible conduit 14 and a fluid passage 15 formed in a connecting member 16, which comprises the lower end of the high pressure chamber 5.

The diaphragm valve 9 is connected to the low pressure chamber 6 by a flexible conduit 17 and a fluid passage 1S formed in a connecting member 19, which comprises the upper end of the low pressure chamber 6.

The check valve 10 is built into a connecting member 20, which comprises the lower end of the low pressure chamber 6, and is in fluid communication with fluid passages 21 and 22 formed in the connecting member 20 whereby it is connected to the low pressure chamber 6 and the core receiving chamber '7, respectively.

, The lower portion of the casing l, beginning at a point below the connecting member 19 and extending downwardly through the low pressure chamber 6, the core receiving chamber 7, and the outer shoe 3, is of hollow, double wall construction, The hollow space between the double walls, indicated by the numeral 23, is sealed, whereby it is air tight, and a partial vacuum is applied thereto, by evacuation of air therefrom, so that the interior of the casing l is insulated against transfer of heat to and from the exterior thereof. This arrangement minimizes freezing of well fluids, as wel] as the earth formation, surrounding the casing il, and tends to concentrate the refrigerating action of the expanding gas on the portion of the formation immediately ahead of the core bit and the core sample already drilled.

A valve 24, which is positioned above the connecting member 19, is in fluid communication with a fluid passage 25 formed in the connecting member 19. The fluid passage 25 is connected by a flexible conduit 26 to the annular spacelj betweenfthe-'double walls of'the casing 1,.and the arrangementis such that air. may. be exhaustedr from the annular space 23 by applying a suction to the valve 24.

The: invention: may." be: modified ini variousff ways-:Withff ontrdepartirrg from the spiritand'scopefthereof;

1; Iwatcore barreltforsuse inobtaining samplestofsubsurfacezearth.- formationsefrom .well bores; the coinbina-V tieni of au coreAv barrel' having a; high. pressurey chambertherein for! therstorage'of; compressed normally gaseous iluid, axlow. pressure chamber positionedbelow the high pressnreichamber for th'e storage. ofliqueiedi gas: maintainediat; a: lower pressure, auidpassage szzorrnnunicatingl ati its ends'witlra the; highl and lowy pressure@ chan'nb'er,` an open-i ended: core` receiving chamber positioned below' the lovv'spressure chamber, aiuid'passagecommunicating atA itsv ends With-they lowpressure chamber/and the core receivingloliamber, a` diaphragmv-alvein the fluidpassage between the high'pressure chamber andthe low-pressurechamberj and'operable'inlresponse to predetermined externalgpressures existing in a Wellbore, whereby a stream of liquefied gas is released from `the high pressure-chain.-

berandpasses through the low pressure chamber, andl is` discharged into the core receiving chamber, as the core barrel approaches the bottom of the Well bore, and a check valve in the iluid passage between the low pressure chamber and the core receiving chamber.

2. A core barrel as described in claim 1 having a cylindrical casing, open at its lower end, enclosing the high pressure chamber, theb 10WA pressure chamber and the core receivingf chamber, at1eastthe lower portiornof.. the easing, below. the. hghfpressure ohambegfbeing formed of double walls having a continuous hollow annular space between them, the annular space being sealed and air tight; a'nd'Jvalve-means in' id 'communication with the annular spacerwherebyrair may, be; evacuated from the annular space to create a partial vacuum therein.

References Cited in the file of this patent UNITED? STATDES PifIENfISi 1,870,696 Taylor Aug. 9; 1932 2,779,195 Simon Jan. 29, 1957. 2,812,160 West et al ...-Nov.'.5`,`,1957l 

